Liquid coloring composition comprising an acid etching agent for a set cementitious surface



United States Patent 3,457,210 LIQUID COLORING COMPOSITION COMPRISING AN ACID ETCHING AGENT FOR A SET CEMEN- TITIOUS SURFACE Fred Markus, 4343 Finley Ave., Apt. 3, Los Angeles, Calif. 90027 No Drawing. Continuation-impart of application Ser. No. 307,037, Sept. 6, 1963. This application Feb. 15, 1967, Ser. No. 616,185

Int. Cl. C09d 3/74 U.S. Cl. 26029.6 12 Claims This is a continuation-in-part of my copending U.S. patent application, Ser. No. 307,037, filed Sept. 6, 1963, now abandoned, for Color Treatment of Cementitious Material.

The present invention comprises a one-step process of coloring cementitious surfaces utilizing a liquid coloring composition which includes an acid etching agent, liquid water-dispersible, alkali-resistant, acid-stable organic polymer-containing vehicle which acts as a binding agent for the composition, an acid-stable, alkali-resistant, waterdispersible coloring agent and a major proportion of water. The composition preferably also includes a watersoluble concrete staining agent. The etching agent is present in a critical concentration range and includes sulfuric acid in a minimum required concentration, while the binding agent is present in a critical concentration ratio with respect to the etching agent. The process has the advantage of accomplishing etching of the substrate, in situ formation of an opacity-imparting film or precipitate utilized as filler, coloring of the substrate and formation of a durable protective colored coating on the substrate in one simple, rapid and economical step.

Several methods are currently used for the color treatment of set concrete and other set cementitious surfaces. In one such method, the cementitious surface is painted. In another method, such surface is chemically stained with a metallic salt, with or without subsequent application of an overying coat of paint.

When either paint or stain is to be applied directly to the cementitious surface, usually such surface must first be etched with acid, such as muriatic acid, to assure a good bonding surface for the paint film and good penetration of the substrate by the stain. The etching process usually leaves a deposit which must be removed, as by a water wash, before the paint can firmly bond to the substrate and before the stain can be applied. In the case of oil base paints, the washed surface also must be thoroughly dried before the paint can be applied.

Even when the paint application is preceded by the described etching, washing and drying operations, the resultant paint film is usually subject to blistering and peeling, as a result of the normal transfer of water and water vapor through the body of the substrate. This condition is particularly prevalent when the usual large amount of fillers are included in the paint. Accordingly, painting of cementitious surfaces is time-consuming and in many cases relatively impermanent. Chemical stains have additional disadvantages in that they do not disguise surface irregularities. Moreover, they are available in only a limited variety of colors.

-It is therefore an object of the present invention to provide an improved and simplified process for the color treatment of set cementitious surfaces.

Another object of the invention is to provide an improved liquid coloring composition for the color treatment of set cementitious surfaces.

Another object of the present invention is to provide a single-step, rapid and economical process for the eliective color treatment of a set cementitious surface, which process eliminates the need for separate etching and washing of such surfaces and which process provides a coating resistant to peeling and abrasion.

Another object of the invention is to provide a liquid coloring composition particularly adapted for the effective color treatment of a set cementitious surface in a single step to provide a peel-resistant and wear-resistant coating.

These and other objects of the invention will be apparent from a study of the following detailed description.

The present invention is briefly described in the first paragraph herein and comprises an improved single step process and an improved composition for the color treatment of cementitious surfaces. The process eliminates conventional preliminary etching, washing and drying operations before coloring of the substrate. The coloring composition includes a minimum minor proportion of sulfuric acid (with orwithout other acids) as the etching agent, a water-dispersible coloring agent compatible with acid as well as alkali, selected water-dispersible, alkali-resistant, acid-stable vehicle which serves as the binding agent, and water as a carrier. Preferably, a watersoluble staining agent is also included. The etching agent and binding agent are present in critical concentrations.

Now referring more particularly to the constituents of the composition, any suitable staining agent useful for staining concrete and other cementitious surfaces can be used, for example, an aqueous solution of one or more metallic salts, such as, e.g., cupric, manganous or ferrous salts of the sulfate or chloride type. Any suitable concentration of the staining agent can be used, usually a low concentration, for example, about 50-150 pounds per 100 gallons of the liquid coloring composition formulation. As particular non-limiting examples, per 100 gallons of coloring compounds, 50 pounds of ferrous sulfate produce a tan shade, while 100 pounds of the same salt produce a rust shade. Similarly, pounds of copper sulfate produce a fairly light green shade, while 150 pounds of that salt produce a fairly dark green shade. Salts of the metallic chloride type (e.g., ferrous chloride, cupric chloride or manganous chloride) are used alone or' in combination with the sulfates; for example, pounds of cupric chloride per 100 gallons of the coloring composition produces a light green color.

The etching agent of the liquid coloring composition must contain at least about 0.5 percent by volume (of the composition) of sulfuric acid, on a 66 Baum sulfuric acid basis, in order to provide the desired results. The etching agent is used in a critical concentration equivalent in etching power to about 0.5-2.5 percent by volume of sulfuric acid (66 Baum). It is believed that the sulfuric acid reacts with free lime and alumina in the cementitious surface to form a complex salt, calcium sulfoaluminate. Other acids in the etching agent are believed to form comparable precipitates. The precipitate is opaque and serves as a filler formed in situ in effective concentration to render the resultant colored film opaque. No addi tional fillers are needed.

When smaller concentrations of the etching agent are used than the critical minimum, insufficient filler is formed in situ to impart the desired opacity to the film formed from the coloring composition of the invention, and insufficient etching of the cementitious surface occurs to open up enough pores of such surface to assure adequate very durable bonding of the coloring composition to such surface. Accordingly, the wear resistance of the film formed by the composition is materially impaired and peeling of the film may occur. Concentrations of etching agent in excess of the specified maximum have the effect of producing an excess amount of filler which in turn, causes inadequate bonding of the film to the substrate and impairs the water vapor permeability of the film, thereby promoting blistering and peeling of the film when the substrate is exposed to moisture.

Preferably, the sulfuric acid is used alone as the etching agent and in a preferred concentration range of about 1.0-1.5 percent by volume (of the composition), based on 66 Baum sulfuric acid.

Certain acids can be used with sulfuric acid in the etching agent, preferably those acids selected from the group consisting of hydrochloric acid, sulfamic acid, p-toluene sulfonic acid, and mixtures thereof. When such other acids are employed with sulfuric acid in the etching agent, their concentration is adjusted so that the total acid concentration of the etching agent has an etching power equivalent to that specified in terms of 66 Baum sulfuric acid, whereby the same etching is providing as if only sulfuric acid were used. In any event, sulfuric acid must be present in the etching agent in at least the specified minimum in order to enjoy all of the desired results.

The coloring agent of the composition is any suitable conventional pigment and in any suitable concentration, preferably a very low concentration, for example, about -50 pounds per 100 gallons of the composition. The pigment may be organic or inorganic, but must be resistant to both acid and alkali, the latter because of the lime present in the cementitious material, and the former because of the presence of the acid in the coloring composition. The pigment must be water-dispersible, because Water is the carrier in the composition. Among suitable pigments of the inorganic type are the oxides of iron, copper, chromium, etc. If a brown, red or yellow color is desired, a ferric oxide pigment may, for example, be used. If a green color is desired, a cupric oxide or chromium oxide pigment may, for example, be used. A White pigment material such as, e.g., titanium dioxide, may be added for the production of light shades, while a black pigment material such as, e.g., pure black iron oxide, may be added for the production of darker shades. Any suitable organic pigment such as toluidine red, phthalocyanine green 01' phthalocyanine blue can also be employed.

The pigment is usually preliminarily dispersed in a suitable concentration of a liquid carrier, such as a watersoluble linseed oil or the like, and then mixed with the other constituents of the composition. For this purpose, a number of water-soluble linseed oils are commercially available, including those comprising polyether derivatives of chemically-modified linseed oil in combination with volatile coupling agents. However, it should be understood that these oils and their equivalents have the disadvantage of adversely affecting the development of a hard durable film if they are used in more than relatively small concentrations. Accordingly, for most purposes such materials are used in concentrations not in excess of about 2-3 percent by volume of the composition.

The binding agent of the composition is a liquid capable of forming a water vapor-permeable film when dried on the cementitious surface. It is water dispersible, alkali resistant and acid stable. For this purpose, certain commercially available organic polymer-containing vehicles are suitable, and are preferably selected from the resinin-water emulsion type vehicles having the requisite properties, for example, certain conventional latexes (high polymer resins in the form of colloidal dispersions in water) such as selected acrylic-polymer emulsions, selected vinyl-acrylic copolymer emulsions, selected polyvinyl acetate copolymer emulsions, and selected styrenebutadiene copolymer emulsions. When calculating the total amount of binding agent in the composition, the amount of suitable carrier for the pigment is included in the calculation.

It will be understood that not all of the commercially available polymer-containing film-forming vehicles which fall in the described classes are suitable as the binding agent. Only those which are not only water-dispersible and alkali-resistant, but also are stable to acids (that is, do not precipitate in the presence of acids) can be used. However, proper selection of such vehicles can easily be made by one ordinarily skilled in the art on the basis of criteria above set forth. It will be further understood that any other types of film-forming resinous liquid vehicles which are effective as binding agents, in addition to those mentioned above, can be used in the present coloring composition, provided that they meet the described requirements, including water dispersibility, alkali resistance and acid stability.

The minimum volume of binding agent utilized in the composition is critical in order to obtain satisfactory results. Thus, the binding agent must have a total solids (non-volatiles) volume content, based on the total volume of the composition, which is in a ratio to the etching agent, that is, the sulfuric acid volume concentration (on the basis of 66 Baum) or its equivalent mixture of sulfuric acid and other acid(s) of at least about 4:1. Obviously, the binding agent must be present in a concentration sufficient to carry the coloring agent and in situ produced filler, form a continuous film and bond to the substrate. Thus, where the minimum amount of etching agent, that is, about 0.5 percent by volume of sulfuric acid (based on 66 Baum sulfuric acid), is used, the binding agent must be present in a total solids volume concentration of at least about 2 percent by volume. When a maximum concentration of etching agent is used, that is, equivalent to about 2.5 percent by volume (based on 66 Baum sulfuric acid), then the minimum total solids content of the binding agent is about 10 percent by volume of the composition. However, it is preferred, for maximum results, to utilize an amount of binding agent which provides a solids content in a ratio to the sulfuric acid equivalent of at least about 5:1.

When a concentration of binding agent is empioyed which provides a solids content less than the described critical minimum, the film formed from the binding agent is materially impaired in its ability to permanently bond to the substrate. Although there is no fixed absolute maximum for the concentration of the binding agent, it is preferred that the volume solids content of the binding agent be not in excess of about 20 percent of the total volume of the composition. Moreover, the binding agent normally must be in a minor volume proportion with respect to the total volume of the coloring composition.

In formulating the coloring composition of the invention, the components are added together with mixing. Thus, the staining agent, if utilized, is usually first dissolved in water in a conventional manner. The amount of water preferably employed is that just sufficient to achieve solution of the staining agent. The etching agent is then added to the staining solution and after the resulting solution has cooled to about room temperature, the coloring agent is then added. Finally, the binding agent is added to provide the finished coloring composition. Such composition is particularly adapted for onestep application to the surface of concrete, gunnite, stucco or other cementitious material for permanent coloring of the surface of the latter.

If the staining agent is omitted, the etching agent is initially added to water, and after cooling of the solution, the remaining ingredients are added as previously described.

The liquid coloring composition is applied to concrete or other cementitious surface by any suitable method, as by brushing it on, spraying it on with suitable equipment, or by rolling it on. The composition is very easy to spread and thus is rapidly applied, and the equipment used for the application can be easily cleaned in water after use. Moreover, the composition dries very rapidly, for example, to the touch in a few minutes so that additional coats of the composition can be applied, if desired, soon after the first coat. The composition covers a very large area of surface so that it is economical. No preliminary treatment of the substrate is needed or desired, other than to free it of dirt and grease, if the substrate is not already clean.

When the coloring composition comes into contact with the cementitious surface, several effects are simultaneously produced. The etching agent reacts with the cementitious surface immediately to etch it just sufiiciently to remove the laitance, or surface film, commonly found thereon, and to open up the pores thereof. Moreover, it produces the precipitate which is utilized as the filler.

The pigment in the coloring agent of the composition imparts the desired color to the precipitate. Due to the presence of the precipitate, the concentration of the pigment can be relatively low in the composition.

The binding agent forms a thin film on the cementitious surface, which film includes the precipitate (filler) and pigment and is relatively hard. Such film binds itself to the cementitious surfaces, because of the open nature of the surface pores of the substrate, and protects the underlying cementitious surface, and any stain coloring imparted thereto. Because the film is water vapor permeable, it does not peel or blister when moisture permeates the substrate. Moreover, due to the usually low pigment and filler concentrations, the binding agent need be used in smaller than usual amounts in the composition. The staining agent, where present, stains the substrate to a desired depth, due to the open pores of the substrate. The net effect is to etch, stain and coat the substrate with a hard, inexpensive permanent colored film. Imperfections in the cementitious surface caused by trowelling or other non-uniformities are concealed because of the opacity of the colored film.

After a cementitious surface colored in accordance with the invention has been subjected to abrasion for a considerable period of time (up to two years or more in normal home use), portions of the protective film, including the pigmented precipitate, may be worn away. However, the stain coloring (which is usually present beneath the film) will not have been effected because of its permanent nature. Consequently, if the pigment and stain are of the same color, there will be only a minimum change in appearance of the cementitious surface, and there will be no immediate need to strip it and recoat it with the coloring composition.

The liquid coloring composition may also optionally contain other ingredients such as added non-plugging, non-alkaline fillers, or fillers produced in situ by adding aluminum sulfate to the composition in, for example,

-30 pound amount per 100 gallons of the composition,

tures of the invention.

EXAMPLE 1 Thirty pounds of green chromium oxide in powdered form were ground into 2.5 gallons of Compound A,

water-soluble, alkali-resistant, chemically stable linseed oil having the following physical properties:

The coloring composition of the invention was then prepared, by mixing all of the above pigment dispersion with the following materials:

Copper chloride lbs. (in 40 gal. water) 150 Compound B ....gal 25 Sulfuric acid (66 Baum) gal 2.

Water: gal. Q.S. to make 100.

1 Compound B is a selected vinyl-acrylic eopolymer emulsion having the following physical properties Total solids 55% minimum, Viscosity 1100-4300 cps. Odor Sweet-slight Color ilky wh e pH 5.5,

Free monomer 0.4%. Average particle size 0.25 micron. Weight per gallon 9.1 lbs.

Solids per gallon 5.05 lbs.

Borax stability Stable. Mechanical stability Stable.

Film properties (a) density1.16 gm./cc.

(b) clarltyclear, water, white. (c) gloss-high. (d) ageing-excellent characteristrcs. (e) film formatlonexcellent.

The copper chloride was placed in 40 gallons of water and the sulfuric acid was added to it, after which the coloring agent and then Compound B, the binding agent, were added all with stirring. The resulting composition was brushed onto a concrete surface to form a thin coating thereon. On drying of the coating, the surface exhibited a uniform, opaque light green color, and no imperfections were noticeable. After a period of abrasive wear of the colored surface, a portion of the colored coating had worn away; the light green stained concrete surface therebeneath was exposed, but only noticeable on very close inspection. No peeling of the colored coating was observed over a one year period.

I E MP E;

The composition of the present invention was prepared in the manner set forthiu Example 1 but substituting 12 pounds of white titanium dioxide, 12 pounds of yellow iron oxide, 4 pounds of brown iron oxide and 4 pounds of green chromium oxide in 2.5 gallons of Compound A as the coloring agent'T his was mixed with the followmg:

Ferrous sulfate lbs. (in 40 gals. of water) 50 Compound B gal 20 Sulfuric acid (66 Baum) gal 1 Water, q.s. to make gal.

The resulting composition was applied to a concrete surface, as in Example 1, to impart a uniform opaque 'tan color thereto, no surface imperfections showing phthalo-cyanine pigments in varying combinations were substituted as pigments in the coloring agent, and Compounds C, D, E and F were substituted as the binding agent, all at the same concentrations as those specified 7 in Example 2 for the respective agents. All of such substitutions yielded comparable results.

Compounds C, D and E are each commercially available water-dispersible, alkali-resistant, acid-stable polymeric vehicles which form hard, water vapor-permeable films, said vehicles having the following composition and physical properties.

Compound C is a commercial available water-dispersible, alkali-resistant, acid-stable, water vapor-permeable film-forming acrylic polymer-in-water emulsion sold commercially under the trademark RHOPLEX AC-34, by Rohm and Haas Company, Philadelphia, Pa., and more particularly described, together with its method of preparation, in US. Patent No. 2,795,564, issued June 11, 1957, said emulsion having the following physical properties:

Solids content percent 46-47 Appearance White milky liquid Weight/gallon lbs 8.9 Specific gravity of solids 1.15

Compound D is a selected polyvinyl acetate copolymer emulsion sold under the trademark CL-202 by Celanese Resins Division, Celanese Coatings Company, Louisville, Ky., specifically a copolymer of vinyl acetate and dialkyl ester of maleie acid or its isomer fumaric acid, wherein the acetate is present in a ratio to the dialkyl ester of about 4:1 and having the following physical properties:

Compound E is a selected styrene-butadiene emulsion having the following characteristics:

Monomer ratio 60/40 Specific gravity (25 C.):

Latex 1.010

Solids 1.02 Solids (percent) 46.0:15 Initial pH 4.0:05 Particle size (microns) 0.2 Stabilizer Nonionic In addition, Compound F, a selected chemically unmodified linseed oil emulsion, having th following physical properties was substituted in a separate test for 25% of Compound B with comparable results:

Solids content --percent wt 601-1 Viscosity (KU) 50-60 pH 7.5-9.0 Average particle size microns 1 Solids (wt./gallon) lbs 8.1 Emulsion (wt/gallon) lbs 8.2 Mechanical stability Excellent Freeze-thaw stability (100 F.) Excellent EXAMPLE 3 A liquid coloring composition identical with that of Example 1, except for the use of only 1 pint of sulfuric acid (66 Baum) as the etching agent, was prepared and tested by the procedure set forth in Example 1. Results were somewhat comparable to those obtained in Example 1, except that the resulting dried coating was transparent, rather than opaque, so that the coatingwa's unattractive in appearance, the surface irregularities-of the substrate being clearly visible. Moreover, insuflicient etching took place to allow permanent bonding of the film to the substrate and to promote optimum staining of the substrate. i

In a subsequent experiment, the sulfuric acid content was increased to 3 gallons, the composition otherwise being the same as that of Example '1. Thecomposition when dried into film form'exhibited some peeling after normal home use for a 3 month period, the water vapor permeability and the bondability of the film having been somewhat impaired by the excessive concentration of in situ-produced filler. In a third experiment, the composition of Example 1 was formulated, except that the amount of Compound B was lowered to 8 gallons. The resulting film exhibited inadequate bonding to the substrate so that peeling occurred within 3 months upon normal home use (including exposure to moisture). i

In a fourth experiment utilizing the composition of Example 2, except that hydrochloric acid of 20 Baum was completely substituted in a 5 gallon amountfor the sulfuric acid, the resulting film exhibited insufficient opacity and decreased bonding of the film to the substrate, peeling occurring in 2 months.

In a fifth experiment, 1 gallon of hydrochloric acid was substituted for 1 gallon of the sulfuric acid in the formula tion of Example 1. The resulting film was satisfactory in all respects and comparable to that of Example 1.

Further experiments established that sulfamic acid and p-toluene sulfonic acid could be substituted for the hydrochloric acid, so long as the sulfuric acid was present in a concentration of at least about 0.5 gallon (66 Baum sulfuric acid) per gallons of the composition.

Examples 1, 2 and 3 and the associated experiments set forth herein clearly establish the criticality of the concentration range of the acid etching agent, the minimum requirement of sulfuric acid in the agent, the necessary minimum ratio of binding agent to the acid etching agent, equivalents for the constituents of the acid etching agent, binding agent, coloring agent and staining agent, and the improved results obtained by the present one-step process utilizing the present coloring composition. The advantages of the process and composition include economy, ease of clean-up, relative permanency of the resultant film, nonpeeling and non-blistering of the film, in situ generation of a controlled concentration of the filler and the ability to accomplish etching, staining and coating in a single operation. Other advantages of the invention are as set forth above.

Although the invention has been describedwith reference to particular embodiments thereof, it will be understood that various changes and modifications may be made therein without departing from the spirit of the invention or the scope of the appended claims. All such modifications and changes as are within the scope of the appended claims form a part of the invention.

What is claimed is:

1. A liquid coloring composition for a set cementitious surface, said composition comprising an acid etching agent including sulfuric acid in a concentration of at least about 0.5 percent by volume, on a 66 Baum basis, said etching agent having an acid concentration equivalent in etching power to about 0.5-2.5 percent by volume of 66 Baum sulfuric acid, liquid water-dispersible, alkali-resistant, acid-stable organic polymer-containing vehicle as a binding agent capable of forming a durable, water vaporpermeable film, said binding agent having a solids concentration in a volume ratio to the sulfuric acid equivalent concentration for said etching agent of at least about 4:1, an acid-stable, alkali-resistant, Water-dispersible coloring agent, and water as a carrier.

2. The coloring composition of claim 1 wherein said composition consists essentially of said binding agent,

water, etching agent, coloring agent and a water-dispersible concrete staining agent.

3. The coloring composition of claim 2 wherein said concrete staining agent is water-soluble and it and said binding agent and said coloring agent are each in a minor concentration in said composition and water is present in a major concentration.

4. The coloring composition of claim 2 wherein said acid etching agent includes at least one member selected from the group consisting of hydrochloric acid, sulfamic acid and p-toluene sulfonic acid.

5. A liquid coloring composition for a set cementitious surface, said composition comprising an acid etching agent including sulfuric acid in a concentration of at least about 0.5 percent by volume, on a 66 Baum basis, said etching agent having an acid concentration equivalent in etching power to about 0.5-2.5 percent by volume of 66 Baum sulfuric acid, as a binding agent a copolymer of vinyl acetate and dialkyl ester of maleic acid or its isomer fumaric acid, wherein the acetate is present in a ratio to the dialkyl ester of about 4:1, said binding agent being capable of forming a durable, Water vapor-permeable film and having a solids concentration in a volume ratio to th sulfuric acid equivalent concentration for said etching agent of at least about 4:1, an acid-stable, alkali-resistant, water-dispersible coloring agent, a water-soluble concrete staining agent, and water as a carrier, the binding agent and coloring agent each being in a minor concentration in said composition and the water being present in a major concentration in said composition.

6. A liquid coloring composition for a set cementitious surface, said composition comprising an acid etching agent including sulfuric acid in a concentration of at least about 0.5 percent by volume, on a 66 Baum basis, said etching agent having an acid concentration equivalent in etching power to about 0.5-2.5 percent by volume of 66 Baum sulfuric acid and styrene-butadiene copolymer emulsion as a binding agent, said binding agent being capable of forming a durable water vapor-permeable film and having a solids concentration in a volume ratio to the sulfuric acid equivalent concentration for said etching agent of at least about 4:1, an acid-stable, alkali-resistant, water-dispersible coloring agent, a water-soluble concrete staining agent, and water as a carrier, the binding agent and coloring agent each being in a minor concentration in said composition and the water being present in a major concentration in said composition.

7. A single-step process for the color treatment of a cementitious surface, comprising the application to a cementitious surface of a liquid coloring composition comprising an acid etching agent containing sulfuric acid in a concentration of at least about 0.5 percent by volume on a 66 Baum basis, said etching agent having an acid concentration equivalent in etching power to about 0.5- 2.5 percent by volume of 66 Baum sulfuric acid, liquid water-dispersi-ble, alkali-resistant, acid-stable organic polymer-containing vehicle as a binding agent capable of forming a durable, water vapor-permeable film, said binding agent having a solids concentration in a volume ratio to the sulfuric acid equivalent concentration for said etching agent of at least about 4: 1, an acid-stable, alkaliresistant, water-dispersible coloring agent, and water as a carrier.

8. The process of claim 7 wherein said composition consists essentially of water, said etching agent, binding agent, coloring agent and water-dispersible concrete staining agent.

9. The process of claim 8 wherein said concrete staining agent is water-soluble and it and said binding agent and said coloring agent are each in a minor concentration and water is present in a major concentration.

10. The process of claim 8 wherein said etching agent includes at least one member selected from the group consisting of hydrochloric acid, sulfamic acid and ptoluene sulfonic acid.

11. A single-step process for the color treatment of a set cementitious surface, comprising applying to a set cementitious surface a coloring composition comprising an acid etching agent containing sulfuric acid in a concentration of at least about 0.5 percent by volume on a 66 Baum basis, said etching agent having an acid con centration equivalent in etching power to about 0'.5-2.5 percent by volume of 66 Baum sulfuric acid, as a binding agent a copolymer of vinyl acetate and dialkyl ester of maleic acid or its isomer fumaric acid, wherein the acetate is present in a ratio to the dialkyl ester of about 4:1, said binding agent being capable of forming a durable, water vapor-permeable film and having a solids concentration in a volume ratio to the sulfuric acid equiva lent concentration for said etching agent of at least about 4:1, acid-stable, alkali-resistant, water-dispersible coloring agent, water-soluble concrete staining agent, and water as a carrier, the concrete staining agent and binding agent each being present in a minor concentration in the composition and water being present in a major concentration in the composition.

12. A single-step process for the color treatment of a set cementitious surface, comprising applying to a set cementitious surface a coloring composition comprising an acid etching agent containing sulfuric acid in a concentration of at least about 0.5 percent by volume on a 66 Baum basis, said etching agent having an acid concentration equivalent in etching power to about 0.5-2.5 percent by volume of 66 Baum sulfuric acid and styrene-butadiene copolymer emulsion as a binding agent capable of forming a durable, water vapor-permeable film, said binding agent having a solids concentration in a volume ratio to the sulfuric acid equivalent concentration for said etching agent of at least about 4:1, acid-stable, alkali-resistant, water-dispersible coloring agent, watersoluble concrete staining agent, and water as a carrier, the concrete staining agent and binding agent each being present in a minor concentration in the composition and water being present in a major concentration in the composition.

References Cited UNITED STATES PATENTS 2,377,593 6/ 1945 Van de Bunte 252-792 2,751,775 6/ 1956 Sergovic. 2,846,295 8/1958 Patterson et al. 156-14 3,098,834 7/1963 Jerabek. 3,186,883 6/1965 Frantzen 252-79.4 3,296,169 1/ 1967 Corey. 3,297,612 1/1967 Lee et al.

FOREIGN PATENTS 570,049 2/ 1959 Canada.

OTHER REFERENCES Scripture, Painting Concrete Floors, pp. 9 and 10 of the July 1936 issue of Concrete, published at 400 W. Madison St., Chicago.

DONALD E. CZAJA, Primary Examiner R. W. GRIFFIN, Assistant Examiner US. Cl. X.R. 

1. A LIQUID COLORING COMPOSITION FOR A SET CEMENTITIOUS SURFACE, SAID COMPOSITION COMPRISING AN ACID ETCHING AGENT INCLUDING SULFURIC ACID IN A CONCENTRATION OF AT LEAST ABOUT 0.5 PERCENT BY VOLUME, ON A 66* BAUME BASIS, SAID ETCHING AGENT HAVING AN ACID CONCENTRATION EQUIVALENT IN ETCHING POWER TO ABOUT 0.5-2.5 PERCENT BY VOLUME OF 66* BAUME SULFURIC ACID, LIQUID WATER-DISPERSIBLE, ALKALI-RESISTANT, ACID-STABLE ORGANIC POLYMER-CONTAINING VEHICLE AS A BINDING AGENT CAPABLE OF FORMING A DURABLE, WATER VAPORPERMEABLE FILM, SAID BINDING AGENT HAVING A SOLIDS CONCENTRATION IN A VOLUME RATIO TO THE SULFURIC ACID EQUIVALENT CONCENTRATION FOR SAID ETCHING AGENT OF AT LEAST ABOUT 4:1, AN ACID-STABLE, ALKALI-RESISTANT, WATER-DISPERSIBLE COLORING AGENT, AND A WATER AS A CARRIER. 